Recently, development of Micro Aerial Vehicles (MAVs) around the world has been delayed due to limited understandings of the aerodynamics of small aircraft that fly at relatively low speed. Classical aerodynamic theory can provide relatively accurate performance predictions for an aircraft flying at Reynolds numbers larger than approximately one million. However, the emergence of providing remotely piloted vehicles for military surveillance missions during the late seventies led to an increase in research of lower Reynolds numbers aerodynamics (in the range below 500,000).
In the last several years, Micro Aerial Vehicles (MAVs) have formed a new area of aeronautical research. This type of unmanned aircraft is usually defined by take-off weights of typically less than 500 gram and very small dimensions, leading to wingspans smaller than 50 centimeters. Micro Aerial Vehicles operate at significantly low speeds, and their Reynolds numbers range is about 150,000 and lower. The need in providing an efficient MAV (Micro Aerial Vehicle) has recently increased due to a dramatically increasing demand in developing a very small intelligent unmanned air-vehicle for military, police and civilian purposes. Such air-vehicles would be intended to fly over an area of interest, within a few minutes of a user's request, gathering vital real-time information that can be crucial, for example, to the success of police or military missions. In addition, the use of utilizing miniaturized electronics, such as MEMS (Microelectro-mechanical systems), makes it feasible to develop a relatively inexpensive, small and light weight MAV.
Usually, a MAV carries a photo/video camera that is fixed to its aircraft body. By means of this camera, the MAV takes photos and/or shoots video films of the area of interest, above which said MAV is flying. According to the prior art, due to the longitudinal instability of a MAV, the videos/images that are transmitted to a ground control station to be displayed on a computer screen, usually shake to such a degree that they are often useless to the user since no sufficient visual information can be understood. Therefore, the whole concept of developing the MAV may be meaningless, unless the quality of the videos/images that are transmitted to a remote user is relatively good. The above instability problems can further arise because of the low inertia and low weight of the MAV. In addition, due to the fact that a MAV operates at low Reynolds numbers, special attention can be devoted to providing an efficient airfoil configuration of the MAV.
The MAV instability problems have been recognized in the prior art and various MAV configurations have been proposed to provide a solution. For example, BATMAV™ (Wasp III) presented on FIG. 1A is a light weight MAV that weights about 450 gram [g] and has a wingspan of 42 centimeters [cm]. BATMAV™ has been developed by AeroVironment Inc. that is located in the United States. BATMAV™ is a relatively small, electrically powered unmanned aerial vehicle, which is equipped with forward and side-looking color video cameras, as well as a modular forward or side-looking electo-optical infrared payload. BATMAV™ has rechargeable lithium ion batteries, and it can fly for about 45 minutes, without recharging said batteries. CAROLO™ P50 is another small and light weight MAV as illustrated in FIG. 1B, has a wingspan of 50 [cm] and mass of 550 [g]. CAROLO™ P50 has been developed by Mavionics GmbH company, located in Germany. CAROLO™ P50 can fly, without recharging its batteries, for about 30 minutes.
MIRADOR™ is still another small and light weight MAV as shown in FIG. 1C, having a wingspan of 50 [cm] and a mass of more than 500 [g]. MIRADOR™ has been developed by the ONERA defense aerospace research laboratory, located in France. MIRADOR™ can fly, without recharging its batteries, for about 30 minutes. BLACK WIDOW™ is a further small and light weight MAV, which has a mass of only 50 [g]. The BLACK WIDOW™ has been developed by AeroVironment Inc. (located in the United States), and is designed in a circular platform, as illustrated in FIG. 1D. The BLACK WIDOW™ is powered by an electric motor that accelerates it to a maximum flight speed of 20 m/sec [meters per second]. In addition, the BLACK WIDOW™ can fly, without recharging its batteries, for about 30 minutes; it has a flight range of 17 kilometers at cruising airspeeds between 38 to 53 km/h [kilometers per hour].
US 2007/0029440 discloses an aircraft arrangement for mini or micro UAV comprising a fore wing and an aft wing in tandem closed-coupled arrangement. The aft wing has side panels and control surfaces, and tapered platform with positive sweep, while the fore wing has non-positive trailing edge sweep. The fore wing and the aft wing are disposed at different heights, and the aircraft arrangement has no other wings or tail arrangements.
U.S. Pat. No. 1,987,050 relates to a tailless airplane comprising a continuous wing having a central section with plural engines at its entering edge, said section at cruising and high speeds providing the major lift, and fixed, lateral, swept back stabilizing sections whose centre of pressure is located rearwardly of the centre of pressure of the central section.
U.S. Pat. No. 5,890,441 presents a semi-autonomously directed, autonomously controlled, gyroscopically stabilized, horizontal or vertical take off and landing flying apparatus employing two vertical lift devices equally and longitudinally spaced from the center of gravity of the apparatus; continuously integrated with a drive train apparatus, optional single or multiple power means; congruously connected thereto horizontal thrust devices.
There is a continuous need in the art to provide a MAV, which is relatively stable, especially along its roll (longitudinal) and yaw axes, and has an improved aerodynamic configuration. Also, there is a need to utilize aircraft end plates (connected to both sides of the aircraft) in an effective manner for achieving its stability during the flight and efficiently reducing the induced drag force. In addition, there is a need in the art to overcome vibrations and oscillations along aircraft roll and yaw axes, when the aircraft speed increases, by substantially preventing airflow from a bottom side of an aircraft body to a top side of said body. Further, there is a need to enable shooting relatively stable video scenes and taking relatively stable photos during the aircraft flight by means of an on-board camera.